Influence of Polycarboxylate Superplasticizer and Mineral Additives of Various Nature on the Kinetics of Early Hardening Stages of Cement Systems

Abstract

AbstractInfluence of the polycarboxylate superplasticizer and mineral additives of various natures (siliceous, aluminosilicate, and sulfoaluminate) on the kinetics of early hardening stages of cement systems, characterized by the rate of increase in the plastic strength of cement paste, have been studied with the recording of the following quantitative indicators: the initial and final setting time, time to reach the plastic strength of 5 MPa. The research results showed that the comprehensive use of organic and mineral additives allowed improving positive influence by means of synergetic effect and eliminating the negative influence of each component individually and thereby controlling the properties of cement paste and processes of early structure formation of cement stone. Introducing the carbonate filler (microcalcilte) into non-plasticized cement system (composition No. 5) decelerates the growth of plastic strength to some extent during the first 4 h of hardening as compared to non-modified composition No. 1 (Fig. 2, a). When it replaces 50% of the complex modifier SF+HAM+ESAM (see Table 1, compositions Nos. 7 and 8_1, respectively), it leads to substantial deceleration of both setting time (from 5 to 7.08 h for initial setting time and 6.08 to 8.33 h for final setting time) and the time to reach the plastic strength of 5 MPa (from 7.0 to 9.4 h).Table 1. The studied compositions of cement systems (W/(PC+MAs) = 0.27)Full size table KeywordsCement systemPolycarboxylate superplasticizerMineral additiveSetting timePlastic strength